A CSS-inspired language to select, sequence, and compose DOM events into event streams.
Exports the following method:
Takes an event selector string as input and returns a parsed event stream object definition. The optional source argument takes a string indicating the source value to use by default (normally
"view"). The optional marks argument takes an object whose keys will be treated as the legal mark types, so long as the corresponding values are truthy. For more, see the Vega Event Stream documentation.